Range finder for cameras



Sept 12, 1944- B. E. LUBOSHEZ 2,358,093

RANGE FINDER FOR CAMERAS Filed May 25, 1943 FIGJ.

Patented Sept. 12, 1944 UNITED STATES PATENT OFFICE RANGE FINDER FOR CABIERAS Benjamin E. Luboshez, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application May 25, 1943, Serial No. 488,333

(Cl. SI- 44) Claims.

This invention relates to range finders particularly designed for photographic purposes. One object of my invention is to provide a range finder which is particularly suitable for long, relatively thin cameras. Another object of my invention is to provide an extremely simple type of range finder in` which there are no pivoted parts. Another object of my invention is to provide a range finder which can be `readily intergeared with a camera focusing mechanism, and a still further object of my invention is to provide a range finder which is extremely simple to build, assemble and use. Other objects will appear from the following specification, the novel features being particularly pointed out in the claims at the end thereof. It has been customary in manufacturing range finders to provide a design in which one or more elements are pivotally mounted and moved during the focusing operation. One of the reasons for the cost of this type range finder is that the two reflecting elements, one of which is practically always pivoted have to be made and assembled with extreme accuracy to produce good results. It is, of course, desirable to have as much space as possible between the reflectors or other members forming the base of the range finder and, ordinarily, where the width between the base members is reduced, it is much more difficult to obtain an accurate and sensitive range finder.

In my copending application, Serial No. 487,914 for Inexpensivey range finder, filed May 21, 1943, I have shown a range finder which avoids many of the objections to those before known and which, I believe, is about the simplestI form that a range finder can take. My present invention is for a variation of this range finder since, like it, it utilizes a refracting material. Unlike my application referred to above, the range finder of this application is particularly suited to long. thin or narrow cameras, and it is particularly suited to such cameras employing focusing lenses because it is an extremely simple matter to intergear the camera objective with the range finder so that both will be simultaneously focused.

Coming now to the drawing wherein like reference characters denote like parts throughout:

Fig. 1 is' a top plan view of a typical long, narrow motion picture camera equipped with a range finder constructed with and embodying a preferred form of my invention. The casing surrounding the range nder has been removed;

Fig. 2 is a sectiontaken on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary sectional plan view showing the focusing knob and scale as it would appear when the range finder casing is in place;

Fig. 4 is a rear view of a range finder showing an image of an object which has been correctly focused; and

Fig. 5 shows a second embodiment of my invention in the form of a pocket range finder.

My invention comprises broadly providing a range finder of light refractive material, the base of the range finder being formed byspaced and angularly disposed plane refracting surf aces so positioned that an image being focused upon may be registered on a split field also formed by a pair of crossed and plane refracting surfaces. If the images do not appear registered, one or more refracting surfaces are moved, thereby changing the angular relation of such refracting surfaces to the refracting surfaces forming the split field.

More specifically, I may provide a range finder for a long, relatively narrow camera as shown in Fig. 1. In this figure the camera body I is elongated in shape and has a, front wall 2 supporting a focusing objective 3. On the camera top wall l I provide a range finder which may consist of a single block 5 of light refracting material, such as glass or a clear plastic. The block 5 constitutes a prism which is roughly V-shaped, there being a pair of arms 6 and 'l converging from the front wall 2 toward the rear wall 8. On the front ends -of the arms 6 and l there are light refracting surfaces 9 and I0, and on the rear wall of the prism there are light refracting surfaces II and I2. The normal position of these surfaces is such that an image being focused upon at infinity is brought into registration on the split field I3 formed by the refracting surfaces II and I2. The refracting surfaces 9 and II are preferably in a normal parallel relation and the refracting surfaces I0 and I2 are normally parallel. When parallel, objects at infinity as viewed in the split field I3 will be in registration.

If desired, a spring I4 may tend to move the arms 8 and 'I of the prism apart, but movement is controlled by means of metal pins or inserts I5 and I6 which include right and left-hand nuts into which the right and left-hand screws Wfl. and I8 pass, so that when the knob I9 is turned the arms 6 and 'I may be brought closer together or farther apart, thus altering the angular relationship between the refracting surfaces II) and 9 and their relation to the refracting surfaces II and I2.

I prefer to fasten the prism on the camera top at its rear end only and this maybe done by means of screws 20. Thus, while the back portion of the prism is firmly anchored against movement, it permits the long. forwardly extending arms 6 and'1 to `exthe slight distancerequired for focusing. It should be'remembered that where a mirror is rotated through an angle the reected ray is rotated through twice that angle, whereas where a refracting surface is rotated through an angle the refracted ray is rotated through, not a larger, but a much smaller angle which depends on the material usedand the original angle '.involved. Thus, a range nder of the typewhich have described labove is verymuch lmore sensitive than the more usua1 type in which. a mirror 01u45" prism is mounted.

It is a simple matter :toconnect up vmy irnproved range. finder so that it will focus the camera objective as it'brings an image being focused upon into registration at the split field. QI'his may be vdone by adding a cam 25 to the knob I9, thiscam, as indicated in A1ig.v2. lying inthe path of'an arm Vv2li ofabell crank lever 21 pivoted at `28 `to the camera body and normally turned against thecam by meansof-a spring 29. The knob I9'may be'provided with an inwardly extending pin 30 adapted to strike a pin 3I on the top'wall 4 of the camera to prevent the knob from being turned beyond a predetermined amount infa counter-clockwise direction. the pin 30, by striking the armv'26, preventing too great rotation of theknob in an opposite direction.

The knob I9 preferably carries a scale 3| graduated into units of'distance so that this scale 3I may, as indicated in Fig. -3, indicate when brought opposite toa pointer-.32,the focal setting of thel camera and range nder.

As also indicated vin Fig. y2, the bellcrank lever 21 is provided'with a downwardly extending arm 33 which is vloifurcated-so that thetwo ends 34 project downwardly oneach'side of the camera objective 3 so that they'may havev a pin 35 and slot 36 connection therewith. When the knob I9 is rotated it is obvious that the cam'25 through the bellcrank lever 21 will focus the objective 3.

As indicated in Fig. 2; the prism 5 may be completely covered by a casing or housing 38 which is provided with a rear sighting window 39 opposite the split field I3, as indicated in Fig. 4. and there may be spaced windows 40 and 4I in the front wall of the casing opposite-the light refracting surfaces 9 and I 0. The casing is also provided with a window 42 over the knob I9 so that a portion of the `knoba'nd the focusing scale projects'from the casingfor the focusing operation and for determining the focal setting.

It is not necessary to move'both of the light refracting surfaces 9 and I0 in focusing this type of range nder and,'if desired, only one arm may be moved during the focusing operation. Such a construction is shown in the modification yof'my invention shown in Fig. 5. This iigure illustrates a pocket type of range finder which may consist of acasing U enclosinga prism 5I having a pair of resilient arms 52 and`53. Arm.

52 is provided'with an outer light refracting surface54 behind a window55 and `parallel to a light refracting surface 56 upon the rear of the prism. Arm 53-has a light refractingsurface 51 behind the window 58 light refracting surface 59.

fracting surfaces and parallel to the The two light re- 56 land 59 constitute a split finder is exceedingly .and I2.

`dow 6I in the rear wa1l'62 of the casing.

In this instance the focusing may lbe accomplished by moving only one arm,arm 52 being .here selected. Thisarm is provided witha strap 52 passing about lthe-arm fromv which a pin-52" extends upwardly into a camxslot 63 carried .by the knob 64 mounted -toiturnon the casing upon' a post or stud 65. Theknob 64de providedrwith a pointer 66 which may vindicate on scale graduations 61 the focal setting.

Like the rst form of my invention, this range simple'to use and is, at the same time, accurate. Since'fthexrearend 68'of the range finder isanchored, asby screwsior other fastening 69 to thecasing, .whenthe knobl64 `is turned the light refracting-surface `54 will .move and thereby cause the ima-ge rofx'anobjectl vbeing focused upon to come intoregistration inf the split field 60 when' .the 'knobY has been; turnedvto the proper focal adjustment. It willl benotedin lthis form of myinvention 'that'thearm'SS/is `fixedlyy mounted as byr-ascrew 10 .passing Yinto .camera is that it is usually necessary with known types of range nderslforsuchicameras.to require a numbery of lensesvto vrelay thefimages formed by the base -reiiectors near rthey frontiof such a camera to the :rear of such ay camera. Thus, .range finders for. long :narrowcameras have ordinarily been even more expensivethan range finders for cameras vwhich are more :nearly square or of dimensionsmore vsuitable for the usual range finderconstruction.

While I prefer to form my rangeflnder prism of a single block of `clear plasticxmateriaLbecause I have found that such construction .is the most inexpensive, nevertheless Il may utilize two ormore pieces of material inrmaking up the prism. For instance, .if'the prism isvto be made of glass, it is usually desirable to have the. arms 6 and 1r fer to make the arms 6 andv 1 separatezpiecesof glass, the thickness of the refracting surfaces' II When so made the vparallel surfaces I0 and I2 on one vpiece can be readilyand accurately made parallel iisnecessaryuby` suitable grinding and polishing operations. The :opposite piece with the parallel surfaces and II will be the same shape.asvtherstementioned piece and the two pieces `after' reversingnoneof them may be either cemented. togetherormerely fastened in place as by. the three screws;201'shown in Fig. 1.

Regardless of how the prism is 'made'and of what it is constructed, itv is ofcourse necessary that at least one of the arms of :the prism lbe suiciently resilient to be sprung fthe small amount necessary for focusing'on .near-.byfol `iects. With glass the arms16 andi'1 will always return to their normallpositionglbut I prefer, particularly when the arms of theprism aremade of plasticythat a spring I4 ybe utilized asshown in Fig. l which will always -tend to createcan outward pressure upon'the two farms so that it is not necessary to rely solely on the'resilience relatively thin and consequently I preoi the material to return the refracting surfaces 9 and l0 to their normal position of rest. Of course, the-right andvleit-hand screw construction shownwill hold the arms in any set position, but with' either plastic or glass there is a tendency forthe arms to return to their original rest position, which is usually one in which the surfaces 9 and Il and the surfaces I0 and I2 are all parallel in which position objects at infinity will be brought into registration as indicated in Fig. 4.

In this figure the image consists of the sections I1 and I2` one image appearing on the refractive face Il and the other on the refractive face i2. Thus, the split field I3 permits the images I1 and I2 to appear as a single continuous image. Howevenif the agpole should be moved to a different position relative to the camera, the image I1 would be offset from the image 12. The

operator noticing that the image focused upon was not in focusfwould then turn the dial i9 until the images Il and I2 came into registration as shown in Fig. 4.

I claim:

1. A range findery for photographic purposes, including, in combination, a prism made of material capable of iiexing, a pair of diverging arms on the prism, a split field on the prism formed by light refracting surfaces angularly arranged with respect to each other, one above the other, light refracting surfaces on the ends of the arms and normally parallel to one of the light refracting surfaces ofthe split field, a support carrying the prism, and means movably mounted on the" support and engaging a prism arm for deiiecting the prism arm, whereby the'relative position of images in the split field may be altered.

2. A range finder for photographic purposes, including, in combination, a prism made of material capable of flexing, a pair of diverging arms on the prism, a split field on the prism formed f; by light refracting surfaces angularly arranged including. in combination, a prism made of material capable'of flexing, a pair of diverging arms on the prism., asplit field on the prism formed y by light refracting `surfaces 'angularly arranged v With respect to each other, one above the other,

lightrefracting surfaces on the ends of the arms and normally parallel to one of the light ref fracting surfacesv of the split field` asupport carrying the prism, and a right and a left hand nut, one carried by each prism arm, a right and left hand screw, one engaging one nut and the other engaging the other nut, and means for moving the screws.

4. A range finder for photographic cameras having objectives including, in combination, a prism having a pair of diverging arms, a first pair of light refracting surfaces on the ends of the arms, a second pair of light refracting surfaces on the opposite ends of said arms one normally parallel `to the light refracting surface on the end of one arm and the other normally parallel to the light refracting surface on the end of the other arm, the second mentioned pair of light refracting surfaces lying atleast 'partially one above the other and forming a split field, said prism arms being made ci' a material capable of flexing. and means for fiexing an arm of the prism relatively to the split field thereof.

5. A range finder for photographic cameras having objectives including, in combination, a prism having a pair of diverging arms, a first pair of light refracting surfaces on the ends of the arms, a second pair of light refracting surfaces on the opposite ends of said arms one normally parallel to the light refracting surface on the end of one arm and the other normally parallel t0 the light refracting surface on the end of the other arm, the second mentioned pair of light refracting surfaces lying at least partialy one above the other and forming a split field, said prism arms being made of a material capable of flexing, and means for flexing an arm of the prism relatively to the split field thereof, said means including operable mechanism connecting said means and the camera objective for focusing the objective with the range iinder.

6. A range finder for photographic cameras having objectives including, in combination, a prism having a pair of diverging arms, a first pair of light refracting surfaces on the ends of the arms. a second pair of light refracting surfaces on the opposite ends of said arms one normally parallel to the light refracting surface on the end of one arm and the other normally parallel to the light refracting surface on the end ofthe other arm, the second mentioned pair of light refracting surfaces lying at least partially one above the other and forming a split field, said prism arms being made of a material capable of flexing, and meansA for fiexing an arm of the prism relatively to the split field thereof, said means comprising a movable adjusting knob and a cam and lever mechanism connecting the camera objective and knob for moving the former from the latter.

7. A range finder for long narrow motion picture cameras having front and rear walls and comprising, in combination, a prism, a split field on the prism including a pair of nat angularly disposed light refracting surfaces arranged one above the other in crossed relationship and positioned near the rear wall of the camera, a pair of diverging arms extending from the split eld forwardly toward the front wall of the camera, a light refracting surface on the end of each arm, one angularly disposed light refracting surface of the split field normally lying parallel to one light refracting surface on the end of one arm, the other light refractive surface of the split field normally lying parallel to the light refractive surface on the end of the other arm, and means for varying the angular relation of at least one light refractive surface relative to the others for varying the relationship of images passing through the light refracting surfaces and viewable in the split eld.

8. A range finder for long narrow motion picture cameras having front and rear Walls and comprising, in combination, a prism, a split field on the prism including a pair of fiat angularly disposed light refracting surfaces arranged one above the other in crossed relationship and positioned near the rear wall of the camera, a pair of diverging arms extending from the split held forwardly toward the front Wall of the camera, a light refracting surface on the end of each arm, one angularly disposed light refracting surface of the split eld normally lying parallel to one light refracting surface on the end of one arm, the

other light refractive surface of the split neld normally lying parallel to the light refractive surface on the end of the other arm, and means for varying the angular relation of the two arms relative to the split field for registering images of an object focused upon therei one angularly disposed light refracting surface of the split field normally lying parallel to one light refracting surface on the end of one arm, the other light refractive surface of the split eld normally lying parallel to the light refractive surface on the end of the other arm, and means for varying the angular relation of at least one light refractive surface relative to the other and including an adjustable member directly engaging a prism arm, a mount for the adjustable member on the camera body, a movably mounted lens carried by the camera, mechanism movable by ther adjustable member and operatively engaging the moveably mounted lens carried by the camera body for adjusting the lens with the light refracting surface.

10. A. range finder for long narrow motion picture cameras having front and rear walls and comprising, in combination, a prism, a split eld on the prism including a pair of at angularly disposed light refracting surfaces arranged one above the other in crossed relationship and positioned near the rear wall of the camera, a pair of diverging arms extending from the split eld forwardly toward the front wall of the camera, a light refracting surface on the end of each arm, one angularly disposed light refracting-surface of the split eld normally lying parallel to one light refracting surface on the end of one arm, the other light refractive surface of the split eld normally lying parallel to the light refractive surface on the end of the other arm, and means for varying the angular relation of the two arms relative to the split field for registering images of an object focused upon therein, said means including a movable knob, a cam carried thereby, a pivoted lever engaging the cam, a focusing lens also engaged by the lever whereby movement of the movable knob may simultaneously focus the camera and range nder.

BENJAMIN E. LUBOSHZ. 

